Abstract

Pulmonary emphysema has been redefined as “a condition of the lung characterized by abnormal, permanent enlargement of the airspaces distal to the terminal bronchioles, accompanied by destruction of their walls, without obvious fibrosis”[1]. This diagnosis can theoretically only be established either at autopsy or by examination of surgically resected lobes or lungs. Emphysema is difficult to diagnose accurately during life and almost impossible to quantify. In the 48 autopsy lungs available from the 228 patients who died during the NIH trial of intermittent positive-pressure breathing involving 935 non-hypoxemic patients, Nagai showed that there were no significant relationships between clinical or physiologic variables and either the interalveolar wall thickness or the alveolar surface area, as calculated from measurements of the mean linear intercept [2].